Interior Secretary Ryan Zinke testifies before the Senate Committee on Energy and Natural Resources during a committee hearing on the President's Budget Request for Fiscal Year 2019, Tuesday, March 13, 2018, on Capitol Hill in Washington. (AP Photo/Jacquelyn Martin)

Interior Secretary Ryan Zinke arrives to testify before the Senate Committee on Energy and Natural Resources at a committee hearing on the President's Budget Request for Fiscal Year 2019, Tuesday, March 13, 2018, on Capitol Hill in Washington. At right is Olivia Barton Ferriter, with the Interior Department. (AP Photo/Jacquelyn Martin)

Interior Secretary Ryan Zinke testifies before the Senate Committee on Energy and Natural Resources during a committee hearing on the President's Budget Request for Fiscal Year 2019, Tuesday, March 13, 2018, on Capitol Hill in Washington. (AP Photo/Jacquelyn Martin)

WASHINGTON (AP) — Interior Secretary Ryan Zinke bristled Tuesday under questioning by Democrats about his travel spending as the Trump administration seeks deep cuts to conservation programs and fee increases at national parks.

Zinke testified before a Senate committee about the agency's proposed $11.7 billion budget for 2019.

He has proposed doubling entry fees during peak seasons at some of the nation's most popular national parks to help make up for an $11 billion backlog in needed maintenance. Meanwhile, an Interior advisory committee has proposed cutting royalty fees paid by energy companies to drill for oil and natural gas in federal waters.

The former Navy SEAL flashed with anger when the Energy and Natural Resources Committee's ranking Democrat pressed him on whether he could justify increasing access fees for working Americans when he has been spending taxpayer money on chartered airplane flights. Sen. Maria Cantwell of Washington asked Zinke if it was a mistake for him to spend $12,375 on a late-night trip in June from Las Vegas to his home state of Montana on a private jet.

"Well, first, insults and innuendos are misleading. I never took a private jet anywhere," Zinke said, adding that all three flights he had taken on private planes as secretary were on aircraft driven by propellers, not jet engines.

Zinke also referenced a report last week by The Associated Press that the Interior Department is spending nearly $139,000 to upgrade three sets of double doors in his office at the agency's headquarters.

"I resent the fact of your insults, I resent the fact they're misleading, I resent the fact of the doors," Zinke said to Cantwell, the tone of his voice growing sharp. "And I'll go through line by line. ... To allege that it's a private jet is inappropriate, ma'am."

Zinke is one of several members of President Donald Trump's Cabinet who have been under intense scrutiny for spending on travel and other expenses that critics deemed questionable. Records show he also spent more than $53,000 on three helicopter trips last summer, including one that allowed him to return to Washington in time to take a horseback ride with Vice President Mike Pence.

Zinke has previously derided the flap over his pricey flights as "a little BS" and pointed to flights taken by former Interior Secretary Sally Jewell during the Obama administration.

Sen. Ron Wyden, D-Ore., told Zinke he has fallen far short of his self-professed role model, Theodore Roosevelt, a renowned conservationist who protected about 230 million acres of public lands. By contrast, Zinke "pushed the largest reduction of ... treasured public lands in American history," proposed opening most of America's coasts to offshore oil drilling and "played a shell game" with wildfire budgeting during the most expensive wildfire season in U.S. history, Wyden said.

Wyden, who has served in Congress for nearly four decades, called his vote to confirm Zinke "one of the biggest regrets of my time in public service."

Interior's inspector general is investigating Zinke's travel and is expected to issue a report within a few weeks.

It is not the first time Zinke has faced questions over his travel spending. A 1999 report by the Navy faulted Zinke for improper travel expenses submitted for two flights to Montana while he was an officer, including one for which he reimbursed the Navy for $211.

Zinke told The Associated Press in 2014 that the travel disputes occurred because his commanding officer disagreed with his belief that Montana should be used for SEAL training.

At Tuesday's hearing, Zinke also defended proposed increases to national park entrance fees and downplayed the possibility of oil and gas exploration off the Pacific coast, where officials in California, Oregon and Washington are adamantly opposed.

The coasts of Oregon and Washington and most of California have "no known resources of any weight," Zinke said.

Likewise, Maine has little recoverable oil and gas off its coast, Zinke said.

Zinke's proposal to open 90 percent of the nation's offshore reserves to development has sparked widespread opposition along the East and West coasts.

Zinke's plan to charge $70 per vehicle at some of the busiest national parks — including Yellowstone, Grand Canyon, Yosemite and Zion — also has drawn fierce opposition. Currently, the Park Service charges entry fees of $25 or $30 per vehicle.

"When you give discounted or free passes to elderly, fourth graders, veterans, disabled, and you do it by the carload, there's not a whole lot of people who actually pay at our front door," Zinke said. "So, we're looking at ways to make sure we have more revenue in the front door of our parks themselves."

The Park Service increased the cost of a lifetime pass for seniors last year from $10 to $80. An annual pass costs non-seniors $80, an amount Zinke called "the greatest bargain in America."

"I just took my kids to the theater, and after paying the ticket to the theater and having popcorn, it's more than $80," said Zinke, who according to his financial disclosure statements has personal assets worth between $1.8 million and $2.8 million.